Automobile vehicle battery tray with side impact rails

ABSTRACT

A battery tray for a battery powered vehicle includes a battery tray having a side wall. An impact absorbing structure is connected to the side wall. The impact absorbing structure includes at least one roll-formed member fixed to the side wall. The at least one roll-formed member is created from a single metal plate and includes a first plate portion roll-formed to create a first cavity and having a first flange created in a member central wall of the first plate portion. The first flange is fixed to the first plate portion. A second plate portion is roll-formed to create a second cavity and has a second flange at an end of the second plate portion fixed to the member central wall. A roll-formed U-shaped attachment member is fixed to the at least one roll-formed member.

FIELD

The present disclosure relates generally to energy absorbing structuresused in battery trays of battery powered automobile vehicles.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

Automobile vehicles including electric and hybrid vehicles providing atleast partial propulsion from battery power create unique conditionsthat must be considered due to the energy and fluid in the battery cellsto absorb structural impact without battery cell damage. The batterytrays of known battery powered and hybrid or battery-engine poweredvehicles, hereinafter collectively referred to as “battery powered”vehicles, provide features to absorb impact loads from below and fromthe sides of the battery trays to minimize damage to the battery cellsinside, however, the structural designs of such battery trays oftenrequire total replacement of the battery tray following minor structuraldamage, and add significant cost to the battery tray to accommodateimpact loading.

Thus, while current battery powered vehicle tray designs achieve theirintended purpose, there is a need for a new and improved system andmethod to absorb battery tray energy loading while reducing design andconstruction costs.

SUMMARY

According to several aspects, a battery tray for a battery poweredvehicle includes a battery tray body having perimeter side walls. Animpact absorbing structure is connected to each of the side walls. Theimpact absorbing structure includes at least one roll-formed memberfixed to the side wall. The at least one roll-formed member is createdfrom a single metal plate and includes a first plate portion roll-formedto create a first cavity and having a first flange created in a membercentral wall of the first plate portion. The first flange is fixed tothe first plate portion. A second plate portion is roll-formed to createa second cavity and has a second flange at an end of the second plateportion fixed to the member central wall. A roll-formed U-shapedattachment member is fixed to the at least one roll-formed member.

In another aspect of the present disclosure, the first flange is fixedusing multiple spot welds prior to roll forming the second plateportion.

In another aspect of the present disclosure, multiple notches arecreated in the first flange.

In another aspect of the present disclosure, an impact rail defines alowest face of the battery tray with respect to a ground level, theimpact rail provided of a shape-memory alloy material.

In another aspect of the present disclosure, an impact rail defines alowest face of the battery tray with respect to a ground level, theimpact rail supported to the impact absorbing structure using at leastone clip of a shape-memory alloy material.

In another aspect of the present disclosure, the U-shaped memberincludes opposed first and second walls, the first wall having a firstraised rib directed toward the second wall and the second wall having asecond raised rib directed toward the first wall. The first raised riband the second raised rib are directly aligned with each other.

In another aspect, a side rail assembly connected to a battery tray in amotor vehicle is provided. The side rail assembly includes a side impactrail having: a first wall having a first rib, a second wall, the secondwall spaced apart from the first wall, the second wall having a secondrib, and a third wall, the third wall connected to the first wall andthe second wall. The first rib extends towards the second rib and thesecond rib extends towards the first rib.

In another aspect, the first rib is aligned with the second rib.

In yet another aspect, the first rib extends along an entire length ofthe first wall.

In yet another aspect, the second rib extends along an entire length ofthe second wall.

In yet another aspect, the side impact rail is roll-formed from a singleplate of metal.

In yet another aspect, the first wall and the second wall aresubstantially parallel.

In yet another aspect, the third wall is substantially perpendicular tothe first wall and to the second wall.

In yet another aspect, a roll-formed member is configured to beconnected to the vehicle battery tray.

In yet another aspect, the first wall includes a first flange connectedto the roll-formed member and the second wall includes a second flangeconnected to the roll-formed member.

In yet another aspect, the first flange is disposed at a first free endof the first wall and the second flange is disposed at a second free endof the second wall.

In yet another aspect, the first wall, the second wall, and the thirdwall have the same thickness.

In yet another aspect, the second rib has a width greater than a widthof the first rib.

In yet another aspect, the first wall, the second wall, and the thirdwall define an interior of the side impact rail, and wherein the firstrib extends into the interior and the second rib extends into theinterior.

In yet another aspect, the side impact rail is substantially U-shaped.

In yet another aspect, the first rib is disposed centrally along a widthof the first wall and the second rib is disposed centrally along a widthof the second wall.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a bottom plan view of an automobile vehicle having a batterytray according to an exemplary embodiment;

FIG. 2 is a bottom plan view of the battery tray of FIG. 1;

FIG. 3 is a side elevational perspective view of area 3 of FIG. 2;

FIG. 4 is an end perspective view of a B-shaped roll-formed member ofFIG. 3;

FIG. 5 is an end perspective view of a roll-formed member modified fromthe B-shaped roll-formed member of FIG. 4;

FIG. 6 is a side elevational perspective view modified from FIG. 2 toinclude the roll-formed member of FIG. 5;

FIG. 7 is an end perspective view of a U-shaped deflectable memberhaving tunable ribs;

FIG. 8 is a side elevational perspective view modified from FIG. 2 toinclude the U-shaped deflectable member of FIG. 7;

FIG. 9 is an end perspective view of a roll-formed member modified fromFIG. 5 to include multiple tunable slots;

FIG. 10 is an end perspective view of a partial roll-formed B-shapedmember of FIG. 4;

FIG. 11 is an end perspective view of a partial roll-formed member ofFIG. 5;

FIG. 12 is an end perspective view of a partial roll-formed memberhaving slots of FIG. 9;

FIG. 13 is an end elevational view of a partial roll-formed membermodified from the B-shaped roll-formed member of FIG. 4;

FIG. 14 is an end elevational view of a partial roll-formed membermodified from the square-shaped roll-formed member of FIG. 5;

FIG. 15 is a graph depicting force versus displacement for an exemplarystructure lacking a central wall; and

FIG. 16 is a graph depicting force versus displacement for an exemplarystructure providing a central wall.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

Referring to FIG. 1, a vehicle battery system 10 includes a battery unitor battery tray 12 structurally mounted to a vehicle 14. The batterytray 12 includes a tub 13 for receiving at least one and according toseveral aspects multiple individual battery cells within the tub 13which provide an electrical charge as the sole power to propel thevehicle 14, or may provide supplemental power in addition to an engine.The tub 13 is preferably formed as a monolithic unitary structure, suchas by stamping or drawing from a metal sheet to form the entire tub 13.The tub 13 also includes an upper flange 15 that extends outwardly froman upper end of the tub 13 for attachment of the tub 13 to a cover (notshown) or for attachment to side members of the tub 13.

Referring to FIG. 2 and again to FIG. 1, the battery tray 12 furtherincludes a collapsible frame 16 disposed on outer lateral sides of thetub 13. The tub 13 is supported by the collapsible frame 16 as astructural unit and defines an energy absorbing portion. The collapsibleframe 16 can be made for example from one or more materials such asrolled metal plate including steel or aluminum, a combination ofmaterials such as a metal and a polymeric material, a composite materialand material alloys. The collapsible frame 16 may provide one or moreside wall impact absorbing structures or side rail assemblies 18 toconnect the collapsible frame 16 to structure of the vehicle 14. Theside wall impact absorbing structures 18 may each include multipleapertures 20 which individually receive one of multiple fasteners (notshown) to releasably fix the battery tray 12 to the structure of thevehicle 14. An impact rail 22 can be further mounted along a substantiallength of a ground-facing side of each of the side wall impact absorbingstructures 18. The impact rails 22 generally form a lowest face of thebattery tray 12 with respect to a ground level, and therefore provide animpact face of first contact should the vehicle 14 traverse a groundfeature that is contacted by the battery tray 12.

Referring to FIG. 3 and again to FIG. 1, an exemplary one of the sidewall impact absorbing structures 18 is shown. An oppositely positionedside wall impact absorbing structure 18 is similar and is therefore notfurther described herein. Each side wall impact absorbing structure 18includes a first B-shaped roll formed member 24 fixed to a side wall 26of the battery tray 12 and a second B-shaped roll-formed member 28oriented substantially perpendicular to the first B-shaped roll-formedmember 24. Each of the first B-shaped roll-formed member 24 and thesecond B-shaped roll-formed member 28 extend substantially an entirelength of the side wall 26 of the battery tray 12. A roll-formedU-shaped attachment member 30 also extends substantially an entirelength of the side wall 26 of the battery tray 12 and includes a flange32 which is fixed for example using weld joint such as a laser weld 34to an outside facing wall 36 of the first B-shaped roll-formed member24. The U-shaped attachment member 30 also includes a first wall 38extending substantially perpendicular to the outside facing wall 36, anoutside facing second wall 40 and a third wall 42 oriented substantiallyparallel to the first wall 38. The third wall 42 partially overlaps anupward facing wall 44 of the second B-shaped roll-formed member 28 andis fixed to the upward facing wall 44 using a weld such as a laser weld46. The U-shaped attachment member 30 may include the apertures 20through the first wall 38 and the third wall 42 to receive fasteners(not shown) to releasably fix the battery tray 12 to the structure ofthe vehicle 14.

A longitudinal cavity 48 is created between first wall 38, the secondwall 40 and the third wall 42. Multiple baffles or stiffening plates 50are positioned within the cavity 48, with a quantity of the stiffeningplates 50 predetermined by the anticipated impact loading expected to bereceived by the second wall 40. The stiffening plates 50 and theU-shaped attachment member 30 will crush or deflect to absorb an impactload directed toward the side wall 26 of the battery tray 12 to helpprevent damage to the side wall 26 and therefore to components such asthe battery cells located within the battery tray 12. To further enhancea deflection resistance of the stiffening plates 50, each of thestiffening plates 50 may also include a stamped or preformed raisedfeature 52, having any desirable shape. The first B-shaped roll-formedmember 24, the second B-shaped roll-formed member 28, the stiffeningplates 50 and the U-shaped attachment member 30 are fixed together forexample by welding, for example by MIG or laser welding, andcollectively create an impact absorbing structure 54. The impactabsorbing structure 54 is also attached to the tub 13, preferably bewelding, such as MIG or laser welding.

The impact rail 22 is mounted along and extends for the length of aground-facing side of the second B-shaped roll-formed member 28 and maybe fixed for example by welding or through the use of fasteners. Theimpact rails 22 generally form a lowest face of the battery tray 12 withrespect to a ground level. An impact face 56 of the impact rail 22 istherefore positioned below (as viewed in FIG. 3) a lowest face 58 of thetray or tub of the battery tray 12. The impact face 56 defines a face offirst contact should the vehicle 14 traverse a ground feature that iscontacted by the battery tray 12. The impact rails 22 are roll formedsimilar to the first B-shaped roll-formed member 24 and the secondB-shaped roll-formed member 28 which are described in greater detail inreference to FIG. 4.

According to several aspects, the impact rail 22 can be a steel materialsimilar to the plate material used for the roll-formed members, or canbe made using a shape-memory alloy material, including but not limitedto alloys of nickel and titanium. As known, a shape-memory alloy is analloy that “remembers” its original shape such that if deformed, thematerial returns to a pre-deformed shape when heated. If an impact loaddeforms the impact rail 22, subsequent heating of the impact rail 22 canbe performed to return the shape of the impact rail 22 to its originalshape, thereby precluding the need to remove and/or replace the impactrail 22. According to other aspects, shape-memory alloy material canalso be used to form mounting clips 59 used to mount a steel (or other)material impact rail 22 to the impact absorbing structure 54, or to anyof the other impact absorbing structures of the present disclosure, suchthat impact loads that shift the impact rail 22 and deform the mountingclips 59 permit the deformed mounting clips 59 to be repaired withoutreplacement of the steel (or other material) impact rail 22. Accordingto still other aspects, shape-memory alloy material can also be used forany of the roll-formed members or the U-shaped members of the presentdisclosure to provide the same benefit for repair without replacement.

Referring to FIG. 4 and again to FIGS. 1 and 2, the second B-shapedroll-formed member 28 is substantially identical to the firstroll-formed B-shaped roll-formed member 24. Each of the B-shaped membersare formed of a single plate of metal such as steel which is roll-formedand welded as follows. A first plate portion 60 is roll-formed to createa first end wall 62 which is substantially perpendicular to the firstplate portion 60. A next bend is formed in the first end wall 62 tocreate a second plate portion 64 oriented substantially parallel to thefirst plate portion 60. A member central wall 66 is formed by creating abend in the second plate portion 64, followed by formation of a firstflange 68. The member central wall 66 stiffens the central portion ofthe second B-shaped roll-formed member 28 to resist against wallcollapse and to absorb impact energy. To simplify construction andreduce component cost, the first flange 68 is fixed using multipleresistance welds, also known as spot welds to an inner face 70 of thefirst plate portion 60, thereby defining a longitudinal first cavity 72.Spot welds are a faster and less expensive alternative to creating MIG,TIG, or laser welds for intervals or for an entire length of the walls.

The first plate portion 60 is co-planar with a third plate portion 74which is roll-formed after completion of the spot welding operations tocreate a second end wall 76 which is substantially perpendicular to thethird plate portion 74 and is therefore substantially parallel with thefirst end wall 62. A next bend is then roll-formed in the second endwall 76 to create a fourth plate portion 78 which is orientedsubstantially parallel to the third plate portion 74. A second flange 80is roll-formed defining an end of the fourth plate portion 78. Thesecond flange 80 is then fixed to the member central wall 66 therebydefining a longitudinal second cavity 82. The second flange 80 may befixed by welding for example using a laser weld 84 and short filletwelds 86 where accessible.

Referring to FIG. 5 and again to FIG. 4, a collapsible roll-formedmember 88 is also roll-formed from a single plate of steel materialsimilar to the B-shaped roll-formed members discussed above, but ismodified from the B-shaped members such as the second B-shapedroll-formed member 28 to provide a rectangular shaped first portion 90and a generally square second portion 92. A first flange 94 similar tothe first flange 68 is fixed using multiple spot welds prior toformation of a second flange 96, which is then welded similar to thesecond flange 80. A width 98 of the first portion 90 is less than awidth 100 of the second portion 92. A height 102 of the first portion 90can be equal to, greater than or less than a height 104 of the secondportion, allowing the roll-formed member 88 to be tuned or designed toabsorb different amounts of loading force at different locations.

Referring to FIG. 6 and again to FIG. 5 and FIG. 3 an impact absorbingstructure 105 is created similar to the impact absorbing structure 54,having a pair of the collapsible roll-formed members 88, 88′ describedin reference to FIG. 5, oriented substantially 90 degrees with respectto each other. The narrow first portion 90′ of the collapsibleroll-formed member 88′ having width 98 abuts the side wall 26 of thebattery tray 12. The narrow first portion 90 of the collapsibleroll-formed member 88 abuts the bottom facing wall of a roll-formedU-shaped attachment member 106 which is substantially identical to theroll-formed U-shaped attachment member 30. A flange 108 of theroll-formed U-shaped attachment member 106 is fixed for example using aweld joint similar to the laser weld 34 to an outside facing wall of thenarrow portion 90′ of the collapsible roll-formed member 88′. Theroll-formed U-shaped attachment member 106 may also include multiplestiffening plates 110 similar in design and function to the stiffeningplates 50. The impact rail 22 for the impact absorbing structure 105 ismounted along a substantial length of a ground-facing side of the narrowportion 90 of the collapsible roll-formed member 88. The U-shapedattachment member 106 may also include the apertures 20 to receivefasteners (not shown) to releasably fix the battery tray 12 to thestructure of the vehicle 14.

Referring to FIG. 7 and again to FIGS. 3 and 6, a roll-formed U-shapedattachment member or side impact rail 112 is modified from theroll-formed U-shaped attachment member 30 and the roll-formed U-shapedattachment member 106. The roll-formed U-shaped attachment member 112includes a first wall 114, an outside facing third wall 116 and a secondwall 118 oriented substantially parallel to the first wall 114. Thefirst wall 114, the second wall 118, and the third wall 116 define aninterior of the U-shaped attachment member 112. The first wall 114 andthe second wall 118 have substantially equal lengths. The first wall 114further includes a first raised rib 120 extending an entire length ofthe first wall 114, and the second wall 118 further includes a secondraised rib 122 extending an entire length of the second wall 118. Theribs 120, 122 extend into the interior of the U-shaped attachment member112. The first raised rib 120 is oriented downwardly and the secondraised rib 122 is oriented upwardly and are in alignment as viewed inFIG. 7, such that an impact load received in a load direction 124 by thethird wall 116 acting to collapse the roll-formed U-shaped attachmentmember 112 will allow collapse until the first raised rib 120 directlycontacts the second raised rib 122. The first wall 114, the second wall118, and the third wall 116 have the same thickness in order to controlcollapse of the U-shaped attachment member 112. To ensure that an impactload received by the third wall 116 at an angle other than perpendicularto the third wall 116 still permits a controlled wall collapse anddirect contact between the raised ribs 120, 122, the second raised rib122 may include a width 126 which is greater than a width of the firstraised rib 120. The first and second raised ribs 120 and 122 are shownin the central area of the U-shaped attachment member 112, and spacedinward from the apertures 20. However, it is contemplated that the firstand second raised ribs 120 and 122 may be disposed closer to either endof the U-shaped attachment member 112, or even outboard of the apertures20.

A first flange 128 is roll-formed at a free end of the first wall 114,and a second flange 130 is roll-formed at a free end of the second wall118. The first flange 128 is upwardly directed as viewed in FIG. 7,which is opposite to the second flange 130 which is downwardly directedas viewed in FIG. 7.

Referring to FIG. 8 and again to FIGS. 3, 4 and 7, an impact absorbingstructure 133 is modified from the impact absorbing structures 54, 105.The impact absorbing structure 133 includes the roll-formed U-shapedattachment member 112 described in reference to FIG. 7 which providesfor fixed attachment of both the first flange 128 and the second flange130 to an outward facing wall of a collapsible rectangular shapedroll-formed member 132. The roll-formed member 132 may differ from thefirst and second B-shaped roll-formed members 24, 28 by omitting themember central wall 66, thereby developing less resistance tocompression forces received when an impact load is transferred to theroll-formed member 132 from the walls of the roll-formed U-shapedattachment member 112. The impact rail 22 is omitted for clarity.

Referring to FIG. 9 and again to FIGS. 4 and 5, a collapsibleroll-formed member 134 is modified from the B-shaped members such as thesecond B-shaped roll-formed member 28 and the collapsible roll-formedmembers 88 by the addition of one or more notches in the spot weldedflange. According to several aspects, the roll-formed member 134includes a rectangular shaped first portion 136 and a generally squaresecond portion 138, although two rectangular shaped portions can also beprovided similar to the second B-shaped roll-formed member 28. A firstflange 140 similar to the first flange 68 is fixed using multiple spotwelds prior to formation of a second flange 141, which is then seam orlaser welded similar to the second flange 80. The first flange 140includes at least one and according to several aspects multiple notches,including for example a first notch 142, a second notch 144 and a thirdnotch 146. The notches are formed for example by a stamping or diecutting operation prior to roll-forming operations.

A spacing 148 between successive ones of the notches can be constant orcan vary, and a notch width 150 can also remain constant or vary topermit a flexibility of the first flange 140 to be changed or “tuned” asdesired to attenuate different impact loads. According to severalaspects a length of the notches can remain constant or can also vary asdesired to further tune the response of the first flange 140. The secondflange 141 is significantly shorter than the first flange 140 andtherefore may not provide as much flexibility if notches are provided inthe second flange 141, however, one or more notches can also be providedwith the second flange 141 if desired.

Referring generally to FIGS. 10, 11 and 12, partial roll-formed membersare shown after an initial roll-forming step to create a first flange,which is resistance or spot welded to the base plate of the member priorto a next roll-forming step to form a second flange. With specificreference to FIG. 10 and again to FIG. 4, a partial roll-formed secondB-shaped roll-formed member 28 includes the first plate portion 60roll-formed to create the first end wall 62, the next bend formed in thefirst end wall 62 to create the second plate portion 64, the membercentral wall 66 formed by creating a bend in the second plate portion64, and formation of the first flange 68. Multiple resistance or spotwelds 152 are then added to fix the first flange 68 to the first plateportion 60, prior to continued roll-forming of the third plate portion74 shown in FIG. 4.

Referring to FIG. 11 and again to FIG. 5, a partial roll-formed member88 is shown following completion of the square shaped second portion 92.Multiple resistance or spot welds 154 are then added to fix the firstflange 94 to the first plate portion 92, prior to continued roll-formingof the rectangular shaped first portion 90 shown in FIG. 5.

Referring to FIG. 12 and again to FIG. 9, a partial roll-formed member134 is shown following completion of the square shaped second portion138 showing exemplary ones of the first notch 142 and the second notch144. Multiple resistance or spot welds 156 are then added to fix theindividual portions of the first flange 140 separated by the notches tothe plate of the second portion 138, and prior to continued roll-formingof the rectangular shaped first portion 90 shown in FIG. 9.

Referring to FIG. 13 and again to FIG. 4, a roll-formed member 158 ismodified from the second B-shaped roll-formed member 28 of FIG. 4.Roll-formed member 158 provides a first flange 160 similar in design tothe first flange 68 which is spot welded to a first plate portion 162prior to roll forming a second flange 164. To further enhance access forwelding, the second flange 164 is overlapped onto a second plate portion166, which is similar in position to the second plate portion 64, andwelded to the second plate portion 166 instead of being welded to amember central wall 168.

Referring to FIG. 14 and again to FIG. 5, a roll-formed member 170 ismodified from the square-shaped roll-formed member 88 of FIG. 5.Roll-formed member 170 provides a first flange 172, similar to the firstflange 94, spot welded to a first plate portion 174 prior toroll-forming a second flange 176. To further enhance access for welding,the second flange 176 is directed outwardly (to the right as shown inFIG. 14) and therefore oppositely directed with respect to the secondflange 96, and welded onto a member central wall 178.

Referring to FIG. 15 and again to FIG. 8, a graph 180 presents exemplarytest data showing force 182 vs. deformation 184 of the structures. FIG.15 presents impact data for an impact absorbing side structure havingD-shaped or rectangle-shaped roll-formed members 132 which lack a membercentral wall 66. In a curve 186, a maximum force 188 of approximately79.81 kN is observed for this structure.

Referring to FIG. 16 and again to FIG. 15, a graph 190 presentsexemplary test data showing force 192 vs. deformation 194 of exemplarystructures. FIG. 16 presents data for a structure with a B-shapedprofile, for example having a member central wall 66 which provides forhigher forces. In a curve 196, a maximum force 198 of approximately156.75 kN is observed for this structure. FIG. 16 data compared to thedata of FIG. 15 further shows the B-shaped side members absorbsignificantly higher forces and deformation before yielding. For theexemplary application of the battery tray 12, it is advantageous toreduce deformation of the side members.

A battery tray having impact absorbing structures and roll-formedmembers of the present disclosure offers several advantages. Theseinclude the incorporation of roll-formed members which are inexpensiveto produce, use spot-welding fixed connections where possible, andabsorb impact energy in an efficient space envelope. The battery traycan also include shape-memory alloy material in various locations whichallow in-place repair of a damaged component without removal orreplacement of the component or replacement of the entire battery tray.The selective placement of notches in locations such as in connectingflanges provides for impact load “tuning” to vary impact loads which canaccommodated without significant change to the space envelope of theimpact absorbing structure.

Additionally, in the claims and specification, certain elements aredesignated as “first”, “second”, “third”, “fourth”, “fifth”, “sixth”,and “seventh”, etc. These are arbitrary designations intended to beconsistent only in the section in which they appear, i.e. thespecification or the claims or the summary, and are not necessarilyconsistent between the specification, the claims, and the summary. Inthat sense they are not intended to limit the elements in any way and a“second” element labeled as such in the claim may or may not refer to a“second” element labeled as such in the specification. Instead, theelements are distinguishable by their disposition, description,connections, and function. Moreover, the term “substantially” as usedherein includes +/−5 degrees from parallel or perpendicular.

The description of the present disclosure is merely exemplary in natureand variations that do not depart from the gist of the presentdisclosure are intended to be within the scope of the presentdisclosure. Such variations are not to be regarded as a departure fromthe spirit and scope of the present disclosure.

What is claimed is:
 1. A side rail assembly connected to a battery trayin a motor vehicle, the side rail assembly comprising: a side impactrail having: a first wall having a first rib extending entirely across awidth and a length thereof from the first wall; a second wall, thesecond wall spaced apart from the first wall, the second wall having asecond rib extending entirely across a width and a length thereof fromthe second wall; and a third wall, the third wall connected to the firstwall and the second wall, wherein the first rib extends towards thesecond rib and the second rib extends towards the first rib, and whereinthe first rib extends on either side from the first wall.
 2. The siderail assembly of claim 1, wherein the first rib is aligned with thesecond rib.
 3. The side rail assembly of claim 1, wherein the first ribextends along an entire length of the first wall.
 4. The side railassembly of claim 1, wherein the second rib extends along an entirelength of the second wall.
 5. The side rail assembly of claim 1, whereinthe side impact rail is roll-formed from a single plate of metal.
 6. Theside rail assembly of claim 1, wherein the first wall and the secondwall are substantially parallel.
 7. The side rail assembly of claim 1,wherein the third wall is substantially perpendicular to the first walland to the second wall.
 8. The side rail assembly of claim 1, furthercomprising a roll-formed member configured to be connected to thevehicle battery tray.
 9. The side rail assembly of claim 8, wherein thefirst wall includes a first flange connected to the roll-formed memberand the second wall includes a second flange connected to theroll-formed member.
 10. The side rail assembly of claim 8, wherein thefirst flange is disposed at a first free end of the first wall and thesecond flange is disposed at a second free end of the second wall. 11.The side rail assembly of claim 1, wherein the first wall, the secondwall, and the third wall have the same thickness.
 12. The side railassembly of claim 1, wherein the second rib has a width greater than awidth of the first rib.
 13. The side rail assembly of claim 1, whereinthe first wall, the second wall, and the third wall define an interiorof the side impact rail, and wherein the first rib extends into theinterior and the second rib extends into the interior.
 14. The side railassembly of claim 1, wherein the side impact rail is substantiallyU-shaped.
 15. The side rail assembly of claim 1, wherein the first ribis disposed centrally along a width of the first wall and the second ribis disposed centrally along a width of the second wall.
 16. A side railassembly connected to a battery tray in a motor vehicle, the side railassembly comprising: a roll formed side impact rail configured toexhibit the properties of a roll formed tailor welded material, the rollformed side impact rail having: a first wall having a first rib withopposite sides each extending away from the first wall; a second wall,the second wall spaced apart from the first wall, the second wall havinga second rib with opposite sides each extending away from the secondwall; and a third wall, the third wall connected to the first wall andthe second wall, wherein the first rib extends towards the second riband the second rib extends towards the first rib, and wherein the firstrib and the second rib are in alignment.
 17. The side rail assembly ofclaim 16, wherein the first wall and the second wall are substantiallyparallel, and the third wall is substantially perpendicular to the firstwall and to the second wall.
 18. The side rail assembly of claim 17,wherein the first wall and the first rib have the same thickness and thesecond wall and the second rib have the same thickness.
 19. The siderail assembly of claim 1, wherein the second rib has a width greaterthan a width of the first rib.
 20. A battery tray assembly for a batterypowered vehicle, the battery tray assembly comprising: a battery trayhaving a side wall; and an impact absorbing structure connected to theside wall, the impact absorbing structure including: a first memberfixed to the side wall; a side impact rail having: a first wall having afirst rib extending entirely across a width and a length thereof fromthe first wall to form a discrete raised first ridge relative to thefirst wall, the first wall connected to the first member; a second wall,the second wall spaced apart from the first wall, the second wall havinga second rib extending entirely across a width and a length thereof fromthe second wall to form a discrete raised second ridge relative to thesecond wall, the second wall connected to the first member; and a thirdwall, the third wall connected to the first wall and the second wall,wherein the first rib extends towards the second rib and the second ribextends towards the first rib, and wherein the first rib and the secondrib are in alignment.